\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=stealth,scale=1.0]
  \draw[densely dashed](0,0)parabola(3,-4)node[below]{$P$}(0,0)parabola(2,-4)node[below]{$M$}(0,0)parabola(5.5,-4)node[below]{$N$};
  \draw[thick](-1,-4)--(7,-4);
  \fill[ball color=gray](0,0)circle(0.15);
  \fill[ball color=lightgray](-0.3,0)circle(0.15);
  \fill[darkgray](0.02,-0.15)rectangle(-0.02,-0.45);
  \fill[darkgray](-0.38,-0.15)rectangle(-0.42,-0.45);
  \fill[brown](-0.26,-0.35)rectangle(-1.5,-0.2);
  \fill[gray](-0.2,-0.15)--(-0.5,-0.15)--(-0.5,-0.2)--(-0.25,-0.2)--(-0.25,-0.35)--(0.05,-0.35)--(0.05,-0.3)--(-0.2,-0.3)--cycle
  ;
  \fill[darkgray](0.08,-0.15)rectangle(-0.08,-0.25);
  \fill[lightgray](0.04,-0.35)rectangle(-0.04,-0.4);
  \fill[lightgray](-0.36,-0.35)rectangle(-0.44,-0.4);
  \draw[thin,densely dashed,postaction={decorate},decoration={markings,mark={at position 0.75 with {\arrow{>}}}}](-0.3,-0.35)--(-0.3,-4)node[above left]{$O$};
  \draw[thin,densely dashed](0,-0.45)--(0,-4)node[above right]{$O'$};
  \fill[brown!50](-0.5,-0.15)..controls(-0.8,-0.15)and(-1.2,-0.05)..(-1.5,0.15)--(-1.5,-0.2)--(-0.5,-0.2)--cycle;
  \draw[thin,->|](-0.5,-4.3)--(-0.3,-4.3);
  \draw[thin,->|](0.3,-4.3)--(0,-4.3);
  \draw[thin](-0.3,-2)--++(165:0.6)node[above]{重锤线};
  \node at(-0.15,-4.2){$2r$};
\end{tikzpicture}
\end{document}